Method and apparatus for combustion



Jan. l0, 1961 s. DE HAAN 2,967,495

METHOD AND APPARATUS FOR COMBUSTION Filed Sept. 22, 1958 2 Sheets-Sheetl INVENTOR:

SIMON DE HAAN Hls ATTORNEY Jan. l0, 1961 s. DE HAAN METHOD AND APPARATUSFOR COMBUSTION 2 Sheets-Sheet 2 Filed sept. 22. 195s FIG.1I

INVENTORI SIMON DE HAAN HIS vATTORNEY BYZ l-United States Patent()lMETHOD AND APPARATUS FOR COMBUSTION Simon de Haan, Delft, Netherlands,assignor to Shell Oil Company, New York, N .Y., a corporation ofDelaware Filed Sept. 22, 1958, Ser. No. 762,531

Claims priority, application Netherlands Oct. 31, 1957 2 Claims. (Cl.110-22) The invention relates to a method and an apparatus suitable forburning solid fuel substantially comprising a mixture of soot and oiland shaped into soft pellets or globules. A fuel of this kind generallycomprises a mixture of soot and gas oil and optionally a little waterand is obtained by intimately mixing soot liberated from chemicalprocesses with amounts of gas oil, diesel oil or other similarhydrocarbon oil.

As an example of a fuel so formed, reference is made to the solidaggregates of soot and oil formed using as starting material the soot inwater obtained in removing soot produced in the partial combustion ofhydrocarbon with oxygen to form gas mixtures containing hydrogen andcarbon monoxide.

The pellets or globules produced in the above manner generally have anaverage diameter in the range of from approximately 3 to l5 mm.

A fuel of this type may comprise, for example, 35- 80% of gas oil,ifi-60% of soot (carbon), 0-2% of ash and a few percent of water. It ispractically impossible to burn this product in a normal furnace hearth.

It is, therefore, an object of this invention to provide a method andapparatus by which combustion of a fuel of the above type may beeffected.

The instant invention now provides a method by which the'above-mentionedfuel is completely burnt, as well as an apparatus suitable forperforming this method, which -apparatus is of a compact constructionand suitable for connecting, for example, to the front of a normalboiler, furnace or the like.

According to the invention the method of burning this fuel ischaracterized in that the fuel and primary combustion air arecontinuously brought together in a primary chamber in which the oil isgasified and at least partially burnt, while at the same time thepellets or globules disintegrate into smaller particles, and that theresultant mixture which contains substantially all the soot in the fuel,is led by the gas stream to a second chamber to which secondarycombustion air is also supplied, in which second chamber the remainderof the fuel is completely burnt.

The apparatus suitable for carrying out this method is characterizedaccording to the invention by a gasifica-v tion chamber vprovided with afuel supply device and a supply for primary combustion air, whichgasification chamber is in communication with an axially symmetricalcombustion chamber which is provided with a tangential supply forsecondary combustion air, which combus- As a result of the gas l ce K2,967,495

parts; the still unburnt oil vapors then have to burn together with thecarbon in the second stage.

In the apparatus according to the invention the narrowed dischargeopening for the fiue gases prevents particles, e.g. of the size of a fewmillimeters, from being entrained after the second stage with the fluegases in an unburnt or -only partially burnt state; the particles remainin the combustion chamber until they are completely burnt.

The gasification chamber is preferably provided, for example, near thebottom, with a grate situated above the primary combustion air inlet, sothat this air can only enter the gasification chamber via this grate,which is arranged below the fuel supply device.

The gasification chamber is preferably box-shaped and the combustionchamber is of a cylindrical design with a substantially horizontalcenter line, both chambers being in communication through an opening inthe peripheral wall of the combustion chamber, which opening is narrowedand provided with a lip or tongue which hinders the ow of secondarycombustion air to the gasitication chamber.

According tothe invention the combustion chamber may be provided with acircular narrowing which separates the part situated above thegasification chamber from the remainder of the combustion chamber.

The invention will now be described in greater detail with reference tothe drawing showing an embodiment of the combustion apparatus accordingto the invention.v Fig. I is a vertical sectional view of the burnertaken on line I--I in Fig. II, and Fig. Il is a vertical sectional viewtaken on line II-II in Fig. I. Fig. III is a vertical sectional viewtaken on line III--III of Fig. II.

Referring to the figures, 1 is a box-shaped gasification chamber, whilecylindrical co-axial parts 2 and 3 together constitute the horizontalcombustion chamber. The gasification chamber 1 is provided with a fuelsupply device 4 and an air inlet 5 for primary combustion air. Thesecondary combustion air is supplied to the part 2 of the combustionchamber via a tangential air linlet 6; if necessary, further combustionair may also be supplied to the part 3 of the combustion chamber via anair inlet 7,'l The gasification chamber is provided with a grate 8,dis-g posed horizontally and situated between the fuel supply device 4and the air inlet 5. A feed reservoir 9 is kept constantly filled withpellet-shaped fuel; this reservoir i s funnel-shaped and has steep wallsin order to promote', the admission of the fuel to an open vibratingchute 10,` this being desirable in view of the great adhesive powerbetween the particles or globules. Near the gasification,

chamber 1 the vibrating chute 10 discharges into a tube 17 communicatingwith the gasification chamber 1, aI

shut-off element 18 being arranged between the tube 17.'

and the part of the vibrating chute 10 which is outside this tube, whichelement has the form of a valve resting on the fuel. The chute 10 ismounted on hangers 20 so that it-is possible for the chute to be broughtinto vibra" tion relative to the fixed tube 17 by means of thevibra-`ting device 16. Alternatively, the wall of the chute 10 may have aflexible section. Downstream of the valve 18 a supply 11 for compressedair issues into the tubek 17. This compressed air can create anequilibrium ini the tube 17 with the gas pressure in the gasificationchamber, so that gas is prevented from leaking'from this chamber via thefuel supply device. fr

It is also possible to use a single or double screw con-l veyor insteadof a vibrating chute as supply device for1 the fuel, or a supply chuteprovided with guide elements.E

The correct selection of the type of supply device which"l it is desiredto use of course depends on the type of the fuel; the greater thepercentage of gas oil in the fuel pellets, the greater will be thetendency to use a supply Patented Jan. 1o, 196i,

device with moving parts. If the pellets are not too compact, avibrating chute is greatly to be preferred.

The passage between gasification chamber 1 and the part 2 of thecombustion chamber is provided with a lip or tongue 13 which is soshaped and directed that the secondary combustion air which rotatesalong the `peripheral wall of the combustion chamber while passing thepassage is unable to enter the gasification chamber. The combustionchamber which is divided by means of a constricted opening in the twoparts 2 and 3 communicating through a circular opening 14, is alsoprovided with a likewise narrowed opening 15 for the discharge of thecombustion gases.

Y Finally, the gasification chamber 1 is also provided with aninspection and ignition opening 12.

The combustion apparatus operates as follows:

The fuel globules are ledfrom the feed reservoir 9 via the vibratingchute 10 and the tube 17 into the gasication chamber 1 where they findtheir way on to the grate 8. Primary air is led to the gasificationchamber via the air inlet 5; this air passes through the grate and thevelocity and pressure of this air are such that the fuel pellets, or atleast a part thereof, are entrained by the air, in the sense that thepellets dance, as it were, on the grid. The following takes place in thegasification chamber:

(1) Drying and pre-heating of the pellets. v

(2) Evaporation, gasification and partial combustion of the gas oil.

(3) Pulverization and disintegration of the pellets `as a result of theviolent movement of the fuel bedlc'aus'cd by the rapid fiow ofcombustion air through the grate.

Combustion gases enter the combustion chamber via the narrowed openingbetween gasification chamber 1 and part 2 of the combustion chamber, aswell as still unburnt gas oil vapors, which gases and vapors entrain theparticles formed in the gasification chamber during the pulverizationand disintegration of the pellets. The second ary combustion air whichis tangentially supplied via the inlet 6 is mixed with the other mediaand causes a rotation of the contents of the combustion chamber in themanner known in cyclone burners, so that the solid particles movetowards the wall and by colliding therewith disintegrate into stillsmaller particles. In this part of the combustion chamber the gas oil isfurther burnt, the carbon is also partly gasified and the particlessplit up into smaller particles as mentioned above, and in conclusionthe cornbustion of the solid particles is initiated.

Complete combustion is finally effected in the la'st part of thecombustion chamber of any remaining gas oil vapors and carbon monoxideformed, and finally of the fine particles of solid carbon which enterthis part of the combustion chamber under favorable combustionconditionsas regards fineness and temperature. On their helical course through thecombustion chamber theseparticles have sufiicient time to come intocontact4 with air and burn completely. The outlet of the combustionchamber is narrowed to prevent carbon particles near the wall fromleaving the chamber unburnt. Thesharp-edged construction 15 promotes theretention of the still unburnt carbon particles. i

It is unnecessary to add air to the combustion chamber through opening7, if, for example, fuel and combustion air have already been mixed to asufiicient degree in the two preceding stages. Furthermore, theapparatus can be controlled more readily when the combustion air issupplied in two stages only instead of in three.

Nor is it always necessary to divide the combustion chamber into twoparts by means of a constriction, for the combustion will proceedsatisfactorily even without such a constriction. Whether or not aconstriction of this kind is used depends, among other things, on thecomposition of the fuel, since if it contains a relatively smallpercentage of volatile components, the presence of a constriction is anadvantage.

In this case the intensity of combustion of the part 2 of the combustionchamber is very high, as both fuel and air are retained for some timeand a good mixing takes place. This is accompanied by a high temperatureand therefore with much radiation energy which is partially passed tothe gasification chamber 1, promoting the ignition of the fuel; ignitionditiiculties in the gasification chamber when the fuel contains a smallpercentage of volatile components are thus avoided.

If the fuel contains ash with a relatively low melting point, theomission of the constriction will be an advantage, however, becausemolten ash is thus prevented from finding its way onto the grate 8through the opening between the part 2 of the combustion chamber and thegasification chamber 1, and the combustion process is not disturbed.Without the presence of a constriction this ash finds its way on to thebottom ofthe part 3 of the combustion chamber, where a draw-ofi' devicemay or'rn'ay not be arranged. I I

In conclusion it should be noted that the capacityI of ati apparatus asdescribed above is very great, .compared t' known apparatuses for solidfuel, since the grate load this apparatus is approximately 1,200 kg. offuel per square meter of grate surface per hour.

I claim as my invention:

1. A method of burning carbon particles comprising: mixing carbonparticles` with hydrocarbon oil and water to form solid pellets havingan average diameter of 3'-15 mm., feeding said pellets continuously intoa gasification and partial combustion chamber, introducing air into saidchamber, partially burning the pellets with said air in said chamber sothat the pellets disintegrate `inl said chamber, passing the resultingstream of gases and disintegrated pellets upwardly into a second chamberof cylindrical shape, introducing a tangential air stream into saidsecondary chamber whereby further burning of the gases and disintegratedpellets takes placein a horizon; tally axially rotating flame, pattern,thereafter discharging the gases through a narrow axial outlet from saidsecondary chamber.

2. An apparatus for burning solid fuel pellets containing finely dividedcarbon and oil comprising: a gasification chamber, a fuel pellet supplymeans leading into said chamber, a grate in said chamber for supportingfuell pellets in said chamber, a primary air supply means sitilrfl atedbelow said grate, a first cylindrical combustion chamber having it'slongitudinal axis horizontal directly connected to said gasificationchamber and mounted thereon, said two chambers being in communicationthroughan opening in the peripheral wall of said first combustionchamber which opening is narrowedV and provided with a tongue element tohinder the fiow of gases to the gasification chamber from firstcombustion chamber, a tangentially directly secondary air inlet t'olsaid first ccmbustion chamber, a restricted axial outlet piececonnecting said first combustion chamber to a second co-axially mountedcylindrical combustion chamber having a tan gentially directed air inletand a restricted axial outlet piece.

References Cited in the file of this patent` UNITED STATES PATENTS

